Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
But more serious events occurred in 600. The Lusitanians, under the leadership of a chief called Punicus, invaded the Roman territory, defeated the two Roman governors who had united to oppose them, and slew a great number of their troops. The Vettones (between the Tagus and the Upper Douro) were thereby induced to make common cause with the Lusitanians; and these, thus reinforced, were enabled to extend their excursions as far as the Mediterranean, and to pillage even the territory of the Bastulo-Phoenicians not far from the Roman capital New Carthage (Cartagena).
The Romans at home took the matter seriously enough to resolve on sending a consul to Spain, a step which had not been taken since 559; and, in order to accelerate the despatch of aid, they even made the new consuls enter on office two months and a half before the legal time. For this reason the day for the consuls entering on office was shifted from the 15th of March to the 1st of January; and thus was established the beginning of the year, which we still make use of at the present day.
But, before the consul Quintus Fulvius Nobilior with his army arrived, a very serious encounter took place on the right bank of the Tagus between the praetor Lucius Mummius, governor of Further Spain, and the Lusitanians, now led after the fall of Punicus by his successor Caesarus (601). Fortune was at first favourable to the Romans; the Lusitanian army was broken and their camp was taken. But the Romans, partly already fatigued by their march and partly broken up in the disorder of the pursuit, were at length completely beaten by their already vanquished antagonists, and lost their own camp in addition to that of the enemy, as well as 9000 dead.
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Reference address : https://www.ellopos.net/elpenor/rome/4-01-gracchi.asp?pg=4